Field of the Invention
The present invention relates to an image heating apparatus of a fuser that is mounted on an image forming apparatus such as a copying machine using an electrophotographic method and an electrostatic recording method, and a printer; a glossiness imparting apparatus that heats a fixed toner image on a recording material again and thereby enhances glossiness of the toner image; and the like. In addition, the present invention relates to a heater which is used in the image heating apparatus.
Description of the Related Art
As for the image heating apparatus, there is an apparatus that has a cylindrical film, a heater which comes in contact with an inner surface of the film, and a roller which forms a nipping portion together with the heater through the film. When an image forming apparatus that mounts the image heating apparatus thereon continuously prints small-sized sheets of paper, such a phenomenon (temperature rise in paper non-passing part) occurs that a temperature in a region gradually increases in which the paper does not pass in a longitudinal direction of the nipping portion. When the temperature on the paper non-passing part becomes excessively high, the high temperature occasionally gives damage to each part in the apparatus, and when the image forming apparatus prints large-sized sheets of paper in a state in which the temperature has risen in the paper non-passing part, a toner is occasionally offset onto the film at high temperature in a region corresponding to a paper non-passing part in the small-sized paper.
As one method for suppressing the temperature rise in the paper non-passing part, Japanese Patent Application Laid-Open No. 2014-59508 discloses an apparatus that divides a heat generating resistor on the heater into a plurality of groups (heat generation blocks) in a longitudinal direction of the heater, and changes a heat generation distribution of the heater according to the size of a recording material.
Because the recording materials which are used in the apparatus have many sizes, a heater is desired that can form the heat generation distribution which is more suitable for various sizes.